U.S. Pat. No. 4,185,883 (Chown et al.) discloses an optical fiber coupling element that includes a glass sleeve secured to a length of optical fiber. The optical fiber is placed in the glass sleeve, and the sleeve is heated so that it collapses around the fiber to hold the fiber in place.
U.S. Pat. No. 6,883,975 (Clarkin et al.) discloses a ferrule presenting a preferentially “softenable” substance within the bore for reducing fusion temperatures and thus reducing distortion of the ferrule and element fused within.
U.S. Pat. No. 6,282,349 (Griffin) discloses a fiber fused in a ferrule that is the definition of prior art disclosed herein which is an evolutionary step in this product development, albeit the current art contains branching embodiments and applications beyond those anticipated in the prior art. Griffin also discloses the use of a tapered fiber for coupling to laser foci larger than the base fiber core. Tapered fibers are focus parameter dependent, i.e. the taper ratio and angle are only optimum for foci of given diameter and numerical aperture (NA).
Much prior are also exists for lenses formed directly on fibers, primarily for improving coupling in telecommunications applications, but also for beam shaping fiber output. The art disclosed herein can also be viewed.
It is often desirable to employ a ferrule in joining optical components together or when incorporating optical components into other devices. A ferrule is a piece of material (glass, ceramic, polymer, metal or composite) having one or more holes into which components such as optical fibers or capillaries may be inserted, offering added support to the fiber/capillary as well as increased structural strength and facilitate alignment of the fiber/capillary with another, similarly terminated component.
In most cases, adhesives secure components carried within ferrules but adhesives can be problematic due to the difference in chemical and physical properties of the adhesives with respect to the fiber and ferrule and inherent liability of organic compounds to oxidation under relatively minor laser illumination. Adhesive terminated fibers in ferrules also are not truly hermetic and are labile to elevated temperatures and certain chemicals. In some applications, it is desirable to provide a fiber-in-ferrule (or capillary-in-ferrule) that may be immersed within solutions of extreme pH, solvents that degrade adhesives, vacuum or elevated pressure and temperature environs. In many, more routine applications it is desirable to provide a seal to prevent migration of gasses or other contamination from the environment into a package intended to isolate an active device, e.g., a semiconductor laser. Where a fiber must pass through a bulkhead, e.g., from a monitor to within a chemical reaction or process stream, chemical and thermal resistance may be critical in maintaining the system seal.
More germane to the art disclosed herein, a ferrule may also act to redirect overfill energy in fibers used in a high power coupling application such as a industrial welding and medical laser delivery systems as in U.S. Pat. No. 6,282,349 (Griffin).